Soil water potential effector apparatus and uses therof

ABSTRACT

An apparatus for effecting water potential in a water-containing media comprising a water-permeable housing, a volume changing material that can retain water, a compressible insert and a receiver for receiving and transducing a signal, is provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Israeli PatentApplication No. 253540 filed Jul. 18, 2017 and U.S. Provisional PatentApplication No. 62/662,950 filed Apr. 26, 2018, the contents of whichare incorporated herein by reference in their entirety.

TECHNICAL FIELD OF THE INVENTION

The invention relates generally to the field of soil water potential,and in particular to soil water potential effector systems and theirapplications in agriculture.

BACKGROUND OF THE INVENTION

Water content in the soil can be directly determined using thedifference in weight before and after drying a soil sample. This directtechnique is usually referred to as the thermo-gravimetric method (orsimply gravimetric) when expressing water content as weight of waterover weight of dry soil, GWC[lb³lb⁻³] (i.e., the ratio of the mass ofwater present in a sample to the mass of the soil sample after it hasbeen oven-dried (100-110° C.) to a constant weight). On the other hand,the thermo-volumetric method (or simply volumetric) gives the watercontent as the volume of water in a volume of undisturbed soil VWC[ft³ft⁻³] (i.e., volume of water related to the volume of an oven-driedundisturbed sample (soil core)). Although these direct methods areaccurate (±0.01 ft³ ft⁻³) and inexpensive, they are destructive, slow (2days minimum), time-consuming and do not allow for making repetitions inthe same location.

Alternatively, many indirect methods are available for monitoring soilwater content. These methods estimate soil moisture by a calibratedrelationship with some other measurable variable. The suitability ofeach method depends on several issues such as cost, accuracy, responsetime, installation, management and durability.

Depending on the quantity measured, indirect techniques are firstclassified into volumetric and tensiometric methods. While the formergives volumetric soil moisture, the latter yields soil suction or waterpotential (i.e., tension exerted by capillarity). Volumetric techniqueestimates the volume of water in a sample volume of undisturbed soil[ft³ ft⁻³]. This quantity is useful for determining how saturated thesoil is (i.e., fraction of total soil volume filled with the soilaqueous solution). When it is expressed in terms of depth (i.e., volumeof water in soil down to a given depth over a unit surface area (inchesof water)), it can be compared with other hydrological variables likeprecipitation, evaporation, transpiration, and deep drainage.

Tensiometric methods estimate the soil water matric potential thatincludes both adsorption and capillary effects of the soil. The matricpotential is one of the components of the total soil water potentialthat also includes gravitational (position with respect to a referenceelevation plane), osmotic (salts in soil solution), gas pressure orpneumatic (from entrapped air), and overburden components. The sum ofmatric and gravitational potentials is the main driving force for watermovement in soils and other soil-like porous media.

All available tensiometric instruments have a porous material in contactwith the soil, through which water can move. Thereby, water is drawn outof the porous medium in a dry soil and from the soil into the medium ina wet soil. Along with certain advantages such as direct reading andsalinity resistance, tensiometers are known to have limited soil suctionrange (<1 bar); relatively slow response time; they require intimatecontact with soil around the ceramic cup for consistent readings and toavoid frequent discharge (breaking of water column inside), requiresfrequent maintenance (refilling) to keep the tube full of water,especially in hot dry weather.

Thus, there remains a need for a water potential effector system whichis universal, long-lasting; durable, inexpensive and responsive tosubtle changes in soil water content.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present invention toovercome disadvantages of the prior art methods and systems for sensingand measuring soil water potential providing a universal, durable, costeffective, broad range water potential effector apparatus having fastresponse time and capable of responding to subtle changes in soil watercontent.

The water potential effector apparatus of the invention comprises: awater permeable housing comprising a predetermined concentration of anvolume changing material (VCM) capable of retaining water, said VCMconfigured to increase or decrease its volume in response to changes inwater potential of the water containing media, and a compressible insertconfigured to maintain a predetermined inner pressure, wherein the innersurface of the housing is in a direct contact with the VCM, and, whenthe volume of said VCM is increased it becomes operationally engagedwith a receiver, to thereby effect the water potential in thewater-containing media.

According to a first aspect, there is provided an apparatus comprising:

-   -   a. a housing comprising at least one portion that is water        permeable;    -   b. a volume changing material (VCM) capable of retaining water,        wherein the VCM increases or decreases its volume in response to        increased or decreased water concentration respectively, and        wherein the VCM is in direct contact with an inner surface of        the at least one water permeable portion of the housing;    -   c. a compressible insert configured to maintain at least a        predetermined inner pressure within the apparatus; and    -   d. a receiver configured to engage the VCM, compressible insert        or both at or above a predetermined threshold of water        concentration and configured to transduce a signal when engaged,        when disengaged, or both.

According to some embodiments, the VCM fills between 10-90% of thevolume of space inside the housing. According to some embodiments, thecompressible insert fills any space inside the housing not filled by theVCM.

According to some embodiments, the receiver is configured to translate aforce applied by the VCM, compressible insert or both into an electricalor mechanical signal. According to some embodiments, the receivercomprises a pressure sensor, a traveling sensor, a force sensor, avalve, or a gauge.

According to some embodiments, the water permeable portion comprises aporous material. According to some embodiments, the porous media is anatural, synthetic, or a semi-synthetic membrane.

According to some embodiments, the compressible insert comprises agas-filled inner volume.

According to some embodiments, the VCM comprises a hydrogel. Accordingto some embodiments, the VCM comprises a biocide. According to someembodiments, the hydrogel is a biocide.

According to some embodiments, the VCM comprises acrylic acid,methacrylic acid, 2-Bromoacrylic acid, 2-(Bromomethyl) acrylic acid,2-Ethylacrylic acid, Methacrylic acid, 2-Propylacrylic acid, Sodiumacrylate, Sodium methacrylate or derivatives thereof, sodium hydroxide,or homopolymers, heteropolymers or derivatives thereof polymerized witha crosslinker of di-acrylate, di-acrylamide, and di-vinyl.

According to some embodiments, the VCM comprises Alkylacrylamide,N-(3-Aminopropyl)methacrylamide hydrochloride, N-tert-Butylacrylamide,Diacetone acrylamide, N,N-Diethylacrylamide, N,N-Diethylmethacrylamide,N,N-Dimethylacrylamide, N-[3-(Dimethylamino)propyl]methacrylamide,N-Ethylacrylamide, N,N′-Hexamethylenebis (methacrylamide),N-Hydroxyethylacrylamide, N-(Hydroxymethyl)acrylamide,(4-Hydroxyphenyl)methacrylamide, 2-Hydroxypropyl-methacrylamide,N-(Isobutoxymethyl) acrylamide, N-Isopropylacrylamide,N-Isopropylacrylamide, N-Isopropylmethacrylamide, Methacrylamide, orhomopolymers, heteropolymers or derivatives thereof polymerized with acrosslinker of di-acrylate, di-acrylamide, and di-vinyl.

According to some embodiments, the VCM comprises copolymers of maleicanhydride copolymer, polyvinyl alcohol copolymers, cross-linkedpolyethylene oxide, crosslinked carboxymethylcellulose or starch graftedcopolymer.

According to some embodiments, the apparatus of the invention furthercomprises a diaphragm between the VCM, insert or both and the receiver,wherein the diaphragm transfers force from the VCM, insert or both tothe receiver.

According to some embodiments, the apparatus is operatively linked to anirrigation system such that the irrigation system activates or shuts offin response to the transduced signal. According to some embodiments, theapparatus is operatively linked to a soil water potential measuringsystem.

According to some embodiments, the apparatus of the invention is for usein measuring water potential.

According to some embodiments, the apparatus of the invention is for usein effecting the water potential in water-containing media proximal tothe apparatus.

According to another aspect, there is provided a moisture sensorapparatus for measuring water potential at variable depths comprising:

-   -   a. at least one apparatus of the invention;    -   b. at least one variable extender configured to insert the at        least one apparatus into a water containing medium at a        predetermined depth;    -   c. a transmitter configured to wirelessly transmit data        concerning water potential measured by the moisture sensor        apparatus.

According to some embodiments, the moisture sensor apparatus of theinvention comprises a plurality of apparatuses of the invention, whereinthe apparatuses are each separated by the at least one variableextender.

According to some embodiments, the apparatus of the invention furthercomprises a solar panel configured to supply power to the apparatus, andwherein the solar panel is located in a region of the apparatusconfigured to be above ground during operation of the apparatus.

In one embodiment, the concentration of the VCM in the housing is atleast 5%. In another embodiment, the concentration of the VCM is between5% to 90%. In one embodiment, the concentration of the VCM is between10% to 70%. In further embodiment, the concentration of the VCM isbetween 10% to 50%. In yet another embodiment, the concentration of theVCM is between 10% to 30%.

In one embodiment, when the volume of VCM increases, the receiver isconfigured to translate the pressure into an electrical or mechanicalsignal. In one embodiment, the receiver is a piston, a valve, amembrane, a transducer, a load cell, and a gauge.

In one embodiment, the water permeable housing comprises a porous media.In another embodiment, the porous media is natural, synthetic or asemi-synthetic membrane. In one embodiment, the porous media is clay.

In one embodiment the compressible insert comprises a mixture of dilutedhydrogel in water solution. In yet another embodiment, the compressibleinsert comprises an antifreeze salt in the solution of divalent salts.

In one embodiment, the VCM comprises a hydrogel. In one embodiment, theVCM further comprises a biocide. In yet another embodiment, the hydrogelis the biocide. In one embodiment, the VCM further comprises afertilizer. In yet another embodiment, the VCM further comprises ananti-freeze.

In one embodiment, the soil water potential effector apparatus isoperatively coupled to an irrigation system.

In one embodiment, the soil water potential effector apparatus isoperatively coupled to a soil water potential measuring system.

In one embodiment, the invention provides a water potential effectorapparatus comprising: a water permeable housing comprising apredetermined concentration of an volume changing material (VCM) capableof retaining water, the VCM configured to increase or decrease itsvolume in response to changes in water potential of the water containingmedia, wherein the inner surface of the housing is in a direct contactwith the VCM, and, when the volume of the VCM is increased it becomesoperationally engaged with a receiver, and wherein the VCM comprisesacrylic acid, methacrylic acid, 2-Bromoacrylic acid, 2-(Bromomethyl)acrylic acid, 2-Ethylacrylic acid, Methacrylic acid, 2-Propylacrylicacid, Sodium acrylate, Sodium methacrylate or derivatives thereof,sodium hydroxide, homopolymers, heteropolymers or derivatives thereof,polymerized with a crosslinker of di-acrylate, di-acrylamide, anddi-vinyl, to thereby effect the water potential in the water-containingmedia.

In yet another embodiment, the invention further provides a waterpotential effector apparatus comprising: a water permeable housingcomprising a predetermined concentration of an volume changing material(VCM) capable of retaining water, the VCM configured to increase ordecrease its volume in response to changes in water potential of thewater containing media, wherein the inner surface of the housing is in adirect contact with the VCM, and, when the volume of the VCM isincreased it becomes operationally engaged with a receiver, and whereinthe VCM comprises Alkylacrylamide, N-(3-Aminopropyl)methacrylamidehydrochloride, N-tert-Butylacrylamide, Diacetone acrylamide,N,N-Diethylacrylamide, N,N-Diethylmethacrylamide, N,N-Dimethylacrylamide, N-[3-(Dimethylamino)propyl]methacrylamide,N-Ethylacrylamide, N,N′-Hexamethylenebis (methacrylamide),N-Hydroxyethylacrylamide, N-(Hydroxymethyl)acrylamide,(4-Hydroxyphenyl)methacrylamide, 2-Hydroxypropyl-methacrylamide,N-(Isobutoxymethyl) acrylamide, N-Isopropylacrylamide,N-Isopropylacrylamide, N-Isopropylmethacrylamide, Methacrylamide,homopolymers, heteropolymers or derivatives thereof, polymerized with acrosslinker of di-acrylate, di-acrylamide, and di-vinyl, to therebyeffect the water potential in the water-containing media.

In further embodiment, provided a water potential effector apparatuscomprising: a water permeable housing comprising a predeterminedconcentration of an volume changing material (VCM) capable of retainingwater, the VCM configured to increase or decrease its volume in responseto changes in water potential of the water containing media, wherein theinner surface of the housing is in a direct contact with the VCM, and,when the volume of the VCM is increased it becomes operationally engagedwith a receiver, and wherein the VCM comprises copolymers of maleicanhydride copolymer, polyvinyl alcohol copolymers, cross-linkedpolyethylene oxide, crosslinked carboxymethylcellulose and starchgrafted copolymer, to thereby effect the water potential in thewater-containing media.

Additional features and advantages of the invention will become apparentfrom the following drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same maybe carried into effect, reference will now be made, purely by way ofexample, to the accompanying drawings in which like numerals designatecorresponding elements or sections throughout.

With specific reference now to the drawings in detail, it is stressedthat the particulars shown are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentinvention only and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of the invention. In this regard, noattempt is made to show structural details of the invention in moredetail than is necessary for a fundamental understanding of theinvention, the description taken with the drawings making apparent tothose skilled in the art how the several forms of the invention may beembodied in practice. In the accompanying drawings:

FIGS. 1A-1E show a moisture sensor apparatus comprising a liquidpermeable container and a transducer, according to exemplary embodimentsof the disclosed subject matter.

FIGS. 2A-2C show a moisture sensor comprising a wireless transmitter andan antenna, according to exemplary embodiments of the disclosed subjectmatter.

FIGS. 3A-3D show a moisture sensor embedded in an irrigation apparatus,according to exemplary embodiments of the disclosed subject matter.

FIGS. 4A-4C show a moisture sensor comprising a pressure sensor,according to exemplary embodiments of the disclosed subject matter.

FIG. 5 shows multiple moisture sensors located in multiple depths in aspecific area, according to exemplary embodiments of the disclosedsubject matter.

FIG. 6 shows multiple moisture sensors located in multiple locations ina specific area, according to exemplary embodiments of the disclosedsubject matter.

FIGS. 7A-B show a size-adjustable moisture sensor, according toexemplary embodiments of the disclosed subject matter.

FIGS. 8A-C: Diagrams illustrating a cross-section of the water potentialeffector apparatus without compressible insert. (8A) Diagramillustrating the apparatus of the invention when VCM [800] is not fullyswollen. (8B) Diagram illustrating the apparatus of the invention whenthe VCM [800] is swollen. (8C) Diagram illustrating the apparatus of theinvention when the VCM is fully swollen and the force is applied to thediaphragm [802] and the receiver [803].

FIGS. 9A-B: Diagrams illustrating a cross section of the water potentialeffector apparatus with a compressible insert [905]. The opening of thecompressible insert is oriented toward the bottom part of the housing[901]. (9A) Diagram illustrating the apparatus when VCM [900] is swollenand the compressible insert is not compressed. (9B) Diagram showing theVCM fully swollen and the insert compressed.

FIGS. 10A-B: Diagrams illustrating a cross section of the waterpotential effector apparatus with a compressible insert [1005]. Theopening of the compressible insert is oriented toward the top of thehousing [1001] and operationally directly engaged with the receiver[1003]. (10A) Diagram illustrating the apparatus when VCM [1000] isswollen and the compressible insert is not compressed. (10B) Diagramshowing the VCM fully swollen and the insert compressed.

FIGS. 11A-B: Diagrams Illustrating a cross section of the waterpotential effector apparatus with a compressible insert [1105]. Theopening of the compressible insert is oriented toward the top of thehousing [1101] and operationally engaged with the receiver [1103]through a diaphragm [1102]. (11A) Diagram illustrating the apparatuswhen VCM [1100] is swollen and the compressible insert is notcompressed. (11B) Diagram showing the VCM fully swollen and the insertcompressed.

DETAILED DESCRIPTION OF THE INVENTION

Before explaining at least one embodiment of the invention in detail, itis to be understood that the invention is not limited in its applicationto the details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is applicable to other embodiments or of being practiced orcarried out in various ways. Also, it is to be understood that thephraseology and terminology employed herein is for the purpose ofdescription and should not be regarded as limiting.

The present invention discloses a moisture sensor apparatus comprising acontainer made of a liquid permeable material designed to be insertedinto a surface, such as the ground. The container contains a volumechanging material (VCM) configured to change its volume in response toabsorbing liquid permeating via the container. The liquid may be water.Optionally, the apparatus also comprises a second unit removably coupledto the container. The second unit comprises a transducer configured togenerate an electrical signal representing a force being measured by thetransducer. The transducer may be a load cell, a pressure sensor and thelike. The apparatus may also comprise a piston operatively coupled tothe VCM, the piston moves towards the transducer and applies a force onthe transducer when the VCM swells. The transducer is configured tomeasure the force or pressure applied by the piston and to generate anelectrical signal representing the measured force. In some exemplaryembodiments, the apparatus may comprise a wireless transmitter fortransmitting the electrical signal to a remote destination. The optionalelements described herein are not limited merely to the figures orembodiments in which they are listed, but rather may be applied orcombined with any figures or embodiments herein described.

The present invention also discloses a method for receiving electricalsignals from multiple moisture sensor apparatuses and analyze them. Suchanalysis may comprise generating a moisture map according to locationsof the moisture sensors. The second unit may comprise a transducer coversecured to the container, for example via a screw, bolt, hook and loop,Velcro and the like. The second unit can be easily separated from thecontainer, enabling a person installing and using the apparatus toadjust the depth of the container in the surface. Similarly, adjustingthe depth of the container may also be achieved by adding anintermediate hollow element between the transducer and the wirelesstransmitter, which may be required to be placed outside the surface, forexample above the ground. The modularity achieved by the second unitbeing removable from the container enables installing differentcontainers, according to specific needs, for example changing acontainer according to the season, type of liquid absorbing volume (LAV)it is inserted in, type of transducer, and the like.

In some exemplary cases, the moisture sensor of the present invention isembedded in an apparatus for controlling the water supplied to thevicinity of the apparatus according to swelling of the VCM. Theapparatus can thus be used for irrigation. The irrigation apparatus iscoupled with a water source and inserted into the surface in a locationwhich needs to be irrigated, to control the level of water content inthe surface at said location. The surface may be ground, for examplegrass or soil or a surface on which plants or mushrooms grow. In someother cases, the location in the surface can comprise bacteria,microorganisms, or mushrooms which need to be irrigated. In some cases,the location in the ground may comprise animals, for example snails in asnail farm which require a moist soil.

FIGS. 1A-1E show a moisture sensor apparatus comprising a liquidpermeable container and a transducer, according to exemplary embodimentsof the disclosed subject matter. FIG. 1A shows a cross-sectional view,FIG. 1C shows an assembled view of the moisture sensor, FIG. 1D shows anexploded view of the apparatus and FIG. 1E shows an exploded view of thetransducer and the transducer housing. FIG. 1B shows the samecross-sectional view as 1A, but with the addition of a compressibleinsert 105. Reference is now made to FIGS. 1A-E.

The liquid container 101 may be inserted into a surface, or LAV, such asa ground, in order to enable the moisture sensor to sense the moisturelevel of the surface. Liquid container 101 is a housing for the moisturesensor apparatus. Liquid, such as water, permeates from the surface andcomes in contact with the VCM 100 located in the liquid container 101.The liquid container 101 may be made of any water permeable material,such as for a non-limiting example, clay. Only a portion of thecontainer 101 may be water permeable. The VCM 100 swells when contactingthe liquid and pushes piston 130 away from the liquid container 101, andtowards a transducer 140. The transducer senses the force applied by thepiston 130 and converts the force into an electrical signal. Theelectrical signal may be transmitted from the transducer 140 via a cablelocated in tube 142 to a transmitter that sends the signal to a remotelocation. In some other cases, the electrical signal may be saved on amemory unit communicating with the transducer 140. In some embodiments,the transducer is a receiver that receives the signal from the VCM 100or insert 105.

In some cases, the moisture sensor comprises a membrane 125 locatedbetween the VCM 100 and the piston 130, for preventing leakage of theVCM 100 into the electrical components located above the piston 130, forexample the transducer 140. The membrane 125 may be attached to thepiston 130 and move when the piston 130 moves. The piston 130 may moveinside a piston housing 135. The inner sidewalls of the piston housing135 guide the piston 130 towards the transducer 140 and back towards theVCM 100. In some exemplary cases, the external sidewalls of the pistonhousing 135 comprise a screw thread 128. In some embodiments, themembrane is part of a diaphragm. In some embodiments, the membrane is adiaphragm.

In some exemplary embodiments, the apparatus comprises a container cover120 covering an upper portion of the liquid container 101, towards thepiston housing 135. The container cover 120 may be made of a rigid orsemi-rigid material such as plastics or metal. In some exemplaryembodiments, the upper portion of the liquid container 101 is wider thana narrower, lower portion of the liquid container 380. In suchembodiments, the container cover 120 is slid from the bottom of theliquid container 101 upwards. Optionally, the container cover 120 mayhave one or more niches 122 via which liquid may permeate the liquidcontainer 101. The container cover 120 may assist in securing the liquidcontainer 101 to the transducer 140. That is, by threading the upperinner sidewalls of the container cover 120 into the lower portion of thescrew thread 128. Similarly, the upper portion of the screw thread 128is configured to be threaded to a transducer housing 138. The transducerhousing 138 houses the transducer 140 and may be attached to the pistonhousing 135 via screw thread 128. In some cases, the transducer housing138 may be attached to the piston housing 135 using adhesive materials,bolts and the like.

The transducer housing 138 may also be attached to a gasket 145. Thegasket 145 may be used in case the cable passing inside tube 142 isconfigured to reach a component located outside the moisture sensor. Insuch a case, the gasket is configured to seal the aperture of thetransducer housing 138 via which the cable exits towards a remotedevice. Such a remote device may be another sensor, a server, atransmitter and the like. A lateral section 136 of the transducerhousing 138 is configured to house the gasket 145.

FIG. 1B is identical to FIG. 1A, but also shows a compressible insert105 that may maintain at least a predetermined inner pressure with theapparatus. In some exemplary embodiments insert 105 directly contactsmembrane 125. In some embodiments, insert 105 directly contacts piston130. In some embodiments, insert 105 directly contact transducer 140. Insome embodiments, insert 125 is anchored to container 101. In someembodiments, insert 105 is free floating in VCM 100.

FIG. 1C also shows an upper seal 150 for preventing materials andliquids to penetrate the moisture sensor and touch the transducer 140.In some exemplary cases, the upper seal 150 is an integral part of thetransducer housing 138. In some exemplary cases, the lateral section 136is an integral part of the transducer housing 138. FIG. 1D introduces aring 139 connecting the transducer housing 138 and the piston housing135.

FIG. 1E shows an exploded view of the moisture sensor. The exploded viewshows a screw 145 that secures the tube 142 to the transducer 140. Thescrew 145 has a hollow void in which the tube 140 is positioned whenattached to the transducer. The screw 145 may define the direction ofthe tube 142, and thus the direction of the cable that transfers theelectrical signal. The cable and the tube 142 are secured to thetransducer 140 via a hollow void inside the lateral section 136 of thetransducer housing 138.

FIGS. 2A-2C show a moisture sensor comprising a wireless transmitter andan antenna, according to exemplary embodiments of the disclosed subjectmatter. The moisture sensor comprises a liquid container 201 thatcontains VCM 200. The liquid container 201 may be covered, at leastpartially, by container cover 220. Piston 230 moves towards transducer240 according to change in the volume of the VCM 200, according toliquid permeating the liquid container 201. A membrane 225 may separatethe VCM 200 from the piston 230. The piston 230 moves in a pistonhousing 235, surrounding the volume in which the piston 230 moves. Thepiston 230 is in contact with the transducer 240 that measures the forceapplied by the piston 230 and generates an electrical signalrepresenting the measured force. The transducer 240 is located in atransducer housing 238. The transducer housing 238 may be attached tothe piston housing 235, for example via adhesives, bolts and the like.In some cases, the external sidewalls of the piston housing 235 comprisea screw thread, to which both the container cover 220 and the transducerhousing 238 are screwed.

The moisture sensor of FIGS. 2A-2C discloses a wireless transmitter 255connected to the transducer 240. In such a case, the wirelesstransmitter 255 may be located inside the transducer housing 238. Thewireless transmitter 255 is configured to transmit the electrical signalto a remote location, for example to a cloud storage, an internetgateway, a server communicating with multiple moisture sensors, andother sensors at the same network and the like. The manner oftransmitting the electrical signal, for example the specific network,communication protocol, frequency band and the like may be selected by aperson skilled in the art. The wireless transmitter 255 may bephysically attached to the transducer 240 and receive the electricalsignal via connectors. In some other cases, the wireless transmitter 255may be connected to the transducer 240 via communication cable 252. Thecommunication cable 252 may be made of coaxial cable. In some exemplarycases, the wireless transmitter 255 may be secured to the moisturesensor and located externally from the transducer housing 238. In somecases, the wireless transmitter 255 may be removable or replaceable fromthe moisture sensor. In some cases, the wireless transmitter 255 may beconnected to an antenna 260 that outputs the electrical signal. Thewireless transmitter 255 may process the electrical signal received fromthe transducer 240, for example add a destination address to theelectrical signal or reformat the electrical signal according to aformat that fits the antenna 260 or the signal destination or network.In some cases, the transducer housing 238 has a lateral extension 248 asshown in FIG. 2C. The lateral extension is configured to house thecommunication cable 252 in case the communication cable 252 extendslaterally, further than the circular form of the transducer housing 238.In some cases, the lateral extension 248 may be removable from thetransducer housing 238 according to the size and architecture of thecommunication cable 252, the transducer 240 and the wireless transmitter255. In case the lateral extension 248 is removed, a gasket may be usedto seal the hole caused by the removal. Embodiments depicted in FIGS.2A-C may also be performed with a compressible insert, such as has beendescribed herein throughout.

FIGS. 3A-3D show a moisture sensor embedded in an irrigation apparatus,according to exemplary embodiments of the disclosed subject matter. Themoisture sensor comprises a liquid container 301 that contains VCM 300.The liquid container 301 may be covered, at least partially, bycontainer cover 320. Piston 330 moves towards transducer 340 accordingto change in the volume of the VCM 300, according to liquid permeatingthe liquid container 301. A membrane 325 may separate the VCM 300 fromthe piston 330. The piston 330 moves in a piston housing 335,surrounding the volume in which the piston 330 moves. The piston 330 isin contact with the transducer 340 that measures the force applied bythe piston 330 and generates an electrical signal representing themeasured force. The transducer 340 is located in a transducer housing338. The transducer housing 338 may be attached to the piston housing335, for example via adhesives, bolts and the like. In some cases, theexternal sidewalls of the piston housing 335 comprise a screw thread, towhich both the container cover 320 and the transducer housing 338 arescrewed.

The irrigation apparatus comprises a water inlet 364 connected to awater pipe. The water pipe may provide water to multiple irrigationapparatuses. The transducer 340 is operatively coupled to a secondarypiston 375. When the piston 330 moves towards the transducer 340, thetransducer also moves, towards the secondary piston 375. Thetransducer's movement may be in the range of 0.1-20 millimeters. Thetransducer 340 causes the secondary piston 375 to move upwards, thusblocking water from moving towards an irrigation output 385 of theirrigation apparatus. Water may flow from the water inlet 364 towardsirrigation output via secondary passageway 380. Thus, when the secondarypiston 375 to move upwards, according to the volume of the VCM 300 inthe container 301, water cannot flow via the secondary passageway 380 tothe irrigation output 385. When the volume of the VCM 300 decreases, thepiston 330 moves downwards, and as a result the transducer 340 and thesecondary piston 375 move downwards, allowing water to flow via thesecondary passageway 380 to the irrigation output 385.

The irrigation apparatus comprises an irrigation housing 360 configuredto house the water inlet 364, irrigation outlet 385 and the secondarypassageway 380. In some exemplary cases, the irrigation housing 360further comprises a connector output 362 configured to transfer waterfrom the water inlet 364 to another apparatus, for example another waterpipe or another irrigation apparatus. The irrigation housing 360 may beattached to the transducer housing 338, for example via bolt 390inserted in a niche in the bottom portion of the irrigation housing 360.In some other exemplary cases, the irrigation housing 360 may beattached to the piston housing 335 or to the container cover 320.

FIG. 3B shows a lateral cross section of the irrigation apparatus withthe moisture sensor. The lateral cross section shows the communicationtube 342 connected to the transducer 340 and carrying the electricalsignal out of the irrigation apparatus. The hole formed to allow thecommunication tube 342 to extend outwards of the transducer housing 338may be sealed by gasket 345. FIG. 3C shows the irrigation apparatusassembled. The exploded view of FIG. 3D shows two holes 390, 391 locatedat the upper portion of the transducer housing 338, securing theirrigation housing 360 to the transducer housing 338. Embodimentsdepicted in FIGS. 3A-D may also be performed with a compressible insert,such as has been described herein throughout.

FIGS. 4A-4C show a moisture sensor comprising a pressure sensor,according to exemplary embodiments of the disclosed subject matter. Themoisture sensor comprises a liquid container 401 that contains VCM 400.The liquid container 401 may be covered, at least partially, bycontainer cover 420. Pressure transducer 424 detects changes in thevolume of the VCM 400, according to liquid permeating the liquidcontainer 401. The pressure transducer 424 moves in a piston housing435, surrounding the volume in which the pressure transducer 424 moves.The pressure transducer 424 measures the pressure applied directly bythe VCM 400 and generates an electrical signal representing the measuredpressure. A communication tube 427 is connected to the pressuretransducer 424 and enables to carry the electrical signal out of themoisture sensor. The communication tube 427 may be located in atransducer housing 438. The transducer housing 438 may be attached tothe piston housing 435, for example via adhesives, bolts and the like.In some cases, the external sidewalls of the piston housing 435 comprisea screw thread, to which both the container cover 420 and the transducerhousing 438 are screwed. The hole in the transducer housing 438 causedby the communication tube 427 may be sealed by gasket 445. The hole maybe located in the ceiling of the transducer housing 438 or in sidewallsof the transducer housing 438.

FIG. 4C shows an exploded view of the moisture sensor having thepressure transducer 424. The exploded view shows a transducer base 422configured to be inserted into a hole in the piston housing 435. Thetransducer base 422 is attached to a wider block 455. The block 455 iswider than the hole in the piston housing 435 and limits the downwardmovement of the pressure transducer 424, towards the liquid container401. In some exemplary cases, the transducer housing 438 comprises aninner ring 450 configured to secure the block 455. Embodiments depictedin FIGS. 4A-C may also be performed with a compressible insert, such ashas been described herein throughout.

FIG. 5 shows multiple moisture sensors located in multiple depths in aspecific area, according to exemplary embodiments of the disclosedsubject matter. Moisture sensors 522, 524, 526 transfer the electricalsignals, which represent the force applied by the VCM, to a remotedevice 520. The remote device 520 may be able to store the signals,process the signals, generate periodic reports, generate maps thatindicate moisture levels in various locations in a certain area and thelike. The remote device 520 may comprise a wireless transmitter fortransmitting the signals or data generated at the remote device 520 toanother device, or to an internet gateway. The remote device 520 mayalso control irrigation of the areas around the moisture sensors.

At least a portion of the multiple moisture sensors 522, 524, 526 arelocated under the ground surface 510. The multiple moisture sensors 522,524, 526 are configured to measure the moisture level in the vicinity oftree 530. It should be noted that the trees are exemplary only and themultiple moisture sensors may be located in multiple liquid absorbingvolumes (LAVs) or in different locations in a single LAV. In someexemplary cases, the multiple moisture sensors 522, 524, 526 transmitthe electrical signals generated by the transducers using communicationcables 523, 525, 527, respectively. In some other cases, the multiplemoisture sensors 522, 524, 526 may send the electrical signals usinglow-range wireless transmitter, for example a blue-tooth transmitter. Insome exemplary cases, the multiple moisture sensors 522, 524, 526 may bepositioned in various depths under the ground surface 510. For example,multiple moisture sensors may be installed on a single rod inserted intothe ground, one sensor disposed 0.7 meters below ground surface 510 andthe other sensor disposed 1.7 meters below ground surface 510. Thesignals provided by the two sensors installed in various depths mayassist the person in charge of irrigating the plants to optimize theirrigation plan.

FIG. 6 shows multiple moisture sensors located in multiple locations ina specific area, according to exemplary embodiments of the disclosedsubject matter. FIG. 6 shows multiple trees 618, 628, 638. Each of thetrees 618, 628, 638 is associated with one or multiple moisture sensorslocated in the vicinity of the tree. Tree 618 is associated withmoisture sensors 610, 611, 612, tree 628 is associated with moisturesensors 620, 621, 622, and tree 638 is associated with moisture sensors630, 631, 632. The multiple moisture sensors, for example 610, 611, 612,may be in the same depth or in different depths. The multiple moisturesensors of each tree may transmit the electrical signals to a remotedevice associated with a single tree. For example, moisture sensors 610,611, 612 transmit the signals to remote device 615, moisture sensors620, 621, 622 transmit the signals to remote device 625, and moisturesensors 630, 631, 632 transmit the signals to remote device 635. In someother exemplary cases, a single remote device is associated with anentire area, for example associated with 50 trees. Thus, when each treeis associated with 3 sensors, the remote device may receive signals from150 sensors.

FIG. 7A shows a size-adjustable moisture sensor, according to exemplaryembodiments of the disclosed subject matter. The moisture sensor'sheight may be adjusted to enable a user of the sensor to place theliquid container 701 in various depths. For example, the same moisturesensor may be located 20 centimeters below a surface, 50 centimetersbelow a surface and 80 centimeters below a surface. The liquid container701 is coupled to a container cover 720 secured to a first housing 725.The first housing may comprise the piston (not shown) and thetransducer. The first housing 725 is coupled to a second housing 735using a first connector 730. The first connector 730 may be adouble-sided screw, enabling connecting the first housing 725 from belowand connecting the second housing 735 from above. In some embodiments,the first connector is replaced with a moisture sensor apparatus of theinvention. In this way there may be multiple sensors in onesize-adjustable apparatus. The sensor-housing-sensor pattern may berepeated multiple times as depicted in FIG. 7B. Having multiple sensorsin one apparatus allows for simultaneous measuring at different depths.Thus, one apparatus can determine irrigation needs at multiple depths inthe same location. The second housing 735 is coupled to a transmitterhousing extension 745 via second connector 740, which functionssimilarly to the first connector 730. In some embodiments, multiplesensor-housing repeats are incorporated into the apparatus beforetransmitter housing extension 745. Optionally there may be a finalconnector 740 before transmitter housing extension 745, regardless ofthe number of sensors incorporated into the apparatus. In someembodiments, the apparatus comprises at least one sensor. In someembodiments, the apparatus comprises a plurality of sensors. In someembodiments, the apparatus comprises 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10sensors. Each possibility represents a separate embodiment of theinvention. In some embodiments, the more than one sensors are separatedby connectors so that the sensors, when inserted into an LAV are atdifferent depths. In some embodiments, each sensor is at least 0.1, 0.2,0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9, 1, 2, 3, 4 or 5 metersapart. Each possibility represents a separate embodiment of theinvention. Though it is FIG. 7B that depicts an embodiment with multiplesensors in one apparatus, this feature may be applied to any otherembodiment of the invention described herein. The transmitter housingextension 745 is coupled to a transmitter housing 750 that houses thewireless transmitter (not shown). In some cases, the transmitter housing750 is connected to a solar panel 760 installed on the external surfaceof the transmitter housing 750. The solar panel 760 may beelectronically coupled to the wireless transmitter, providing electricalpower to the transmitter. In some embodiments, the solar panel isconfigured to power the apparatus, the sensor, the receiver, thetransmitter, or a combination thereof. In some embodiments, the solarpanel is located in a region of the apparatus configured to be aboveground during operation of the apparatus.

In some exemplary cases, the transmitter housing extension 745 iscoupled to the first housing 725 and the second housing 735 is removed.This way, the person using the moisture sensor can adjust the distancebetween the liquid container 701 and the transmitter and hence the depthof the liquid container in the volume surrounding the moisture sensor.In some other embodiments, the moisture sensor comprises a singlehousing connecting the transducer and the transmitter housing 750, thesingle housing is designed in an adjusted manner, for example as atelescopic pole.

By a first aspect there is provided a water potential effector apparatuscomprising a water permeable housing and a volume changing material(VCM). The invention provides a water potential effector apparatuscomprising a water permeable housing. The water permeable housing [101,201, 301, 401, 701, 801, 901, 1001, 1101] is configured to be insertedinto water containing media, or LAV. In one embodiment, the watercontaining media is soil. In some embodiments, the housing is waterpermeable at at least one portion of the housing. In some embodiments,the entire housing is water permeable. In some embodiments, particularregions of the housing are water permeable. In some embodiments, thebottom of the housing is water permeable. In some embodiments, at leastone portion of the housing is water permeable. In one embodiment thehousing is made of porous media. In some embodiments, the waterpermeable portion or region is made of porous media. In furtherembodiment, the porous media is a natural, synthetic or a semi-syntheticmembrane. In yet another embodiment, the porous media is clay.

In the embodiments of the invention the housing comprises a VolumeChanging Material (VCM) capable of retaining water. In some embodiments,the VCM can absorb water. VCM [100, 200, 300, 400, 800, 900, 1000, 1100]is configured to increase or decrease its volume in response to changesin water potential in the water containing media. In some embodiments,the housing surrounds an area comprising the VCM. In some embodiments,the apparatus of the invention comprises the VCM. In some embodiments,the VCM increases or decreases its volume in response to increases anddecreases in water entering the VCM, respectively. In some embodiments,the VCM increases or decreases its volume in response to increasing anddecreasing water concentration, respectively. In some embodiments, thewater concentration is the concentration of water in the VCM. In someembodiments, the water concentration is the concentration of water isthe water containing media. In some embodiments, the water concentrationis the concentration of water in the VCM, the water containing media orboth. In one embodiment, when water potential in the water containingmedia is increased, the water passes through the housing to the VCM,causing the VCM to increase in volume. In some embodiments, the increasein VCM volume builds the turgor pressure. In one embodiment, when waterpotential in the water containing media decreases, the water exits fromthe VCM through the housing into the water containing media, causing theVCM to decrease in volume. In an embodiment of the invention, the VCM isin direct contact with an inner surface of the housing. In someembodiments, the VCM is in direct contact with the water permeableportion of the housing. In one embodiment, an inner surface of thehousing is coated with the VCM. In some embodiments, the entire innersurface of the housing is in contact with or coated with the VCM. In yetanother embodiment, only a portion of the inner surface of the housingis in a direct contact with the VCM. In some embodiments, only a portionof the inner surface of the housing is coated with the VCM.

In one embodiment of the invention, when the volume of the VCMincreases, it becomes operationally engaged with a receiver [803, 903,1003, 1103]. In some embodiments, the receiver is a transducer [140,240, 340]. In some embodiments, the receiver or transducer is configuredto translate the force applied by the VCM into an electrical ormechanical signal. In some embodiments, the receiver comprises adiaphragm or a membrane. In some embodiments, the VCM contacts thediaphragm or membrane. The receiver of the invention is, withoutlimitation, pressure sensor, force sensor, valve, and a gauge. In someembodiments, the receiver comprises a sensor. In some embodiments, thesensor is configured to sense the volume of the VCM. In someembodiments, the sensor comprises at least one of a pressure sensors, aforce sensor, a valve and a gauge. In some embodiments, the receiver isconfigured to engage the VCM. In some embodiments, the receiver isconfigured to engage the VCM at or above a predetermined threshold ofwater concentration. In some embodiments, the receiver is configured toengage the VCM when it reaches or is greater than a predeterminedvolume. In some embodiments, the receiver is configured to transduce asignal. In some embodiments, the receiver is configured to transduce asignal when engaged. In some embodiments, the receiver is configured totransduce a signal when disengaged. In some embodiments, the receiver isconfigured to transduce a signal when engaged and/or disengaged. In someembodiments, the apparatus of the invention further comprises a receiveras described herein.

In some embodiments, the housing further comprises a compressible insert[105, 905, 1005, 1105] configured to maintain a predetermined innerpressure. In some embodiments, the housing surrounds an area comprisingthe insert. In some embodiments, the apparatus of the inventioncomprises the insert. The insert is configured to change its volume inresponse to the force applied by the VCM. In some embodiments, theinsert is configured to change its volume in response to a force appliedto it. In some embodiments, the insert is configured to maintain apredetermined pressure within the housing. In some embodiments, theinsert is configured to maintain at least a predetermined pressurewithin the housing. In some embodiments, the insert is configured not tobreak under the maximum pressure applied by the VCM. The maximumpressure the VCM can exert would occur when it is 100% saturated withwater. The VCM applies its lowest pressure when it comprises no water.In such conditions the insert takes up its maximum volume within theapparatus and keeps a minimum predetermined pressure within theapparatus. Maintaining such a minimum pressure is advantageous in thatit strengthens the apparatus against potential breakage or deformation.As soil around the apparatus moves or is compressed it can apply aphysical force on the housing of the apparatus. As the housing must bewater permeable, it is over made of a rigid, or not very strongmaterial, such as clay. If a minimum pressure is not maintained in theapparatus, it can more easily deform under pressure from the surroundingsoil, especially if this force is sufficient to overcome the strength ofthe housing.

In some embodiments of the invention, when the volume of the VCMincreases, it pushes on the insert and the insert becomes operationallyengaged with a receiver [803, 903, 1003, 1103]. In some embodiments, thereceiver or transducer is configured to translate the force applied bythe insert into an electrical or mechanical signal. In some embodiments,the insert contacts the diaphragm or membrane. In some embodiments, theinsert and/or VCM becomes operationally engaged with a receiver [803,903, 1003, 1103]. In some embodiments, the receiver or transducer isconfigured to translate the force applied by the insert and/or VCM intoan electrical or mechanical signal. In some embodiments, the insertand/or VCM contacts the diaphragm or membrane.

The insert of the invention may contain gas, liquid, solid, semi-solidmaterial or a combination thereof. In one embodiment of the inventionthe insert is not permeable to gaseous, solid, semi-solid or liquidmedia. In some embodiments, the insert comprises a gas-filled volume. Insome embodiments, the insert is a balloon or bladder filled with a gas,liquid, solid, semi-solid material or a combination thereof. Eachpossibility represents a separate embodiment of the invention. In someembodiments, the insert applies a pressure on the VCM that is notsufficient to pushout water from the VCM. In some embodiments, theinsert applies a pressure on the VCM that is not sufficient to hinderwater's ability to enter the VCM. In some embodiments, at high pressurefrom the VCM the insert applies a pressure on the VCM that may slowentry of water. In some embodiments, this counter pressure of the insertis considered in calibrating the apparatus.

FIGS. 10A and 10B show another embodiment where the opening of thecompressible insert is operatively engaged with the receiver [1003],through direct physical contact. When water permeates into the housing[1001] the volume of the VCM [1000] increases, thus building the turgorpressure inside the housing. The pressure triggers compression of theinsert [1005] (as shown in FIG. 10B), which, in turn, triggers anincrease in the force applied to the receiver [1003]. The configurationof the insert [105, 1005, 1105] illustrated in FIGS. 1B, 10A-B and11A-B, is particularly advantageous since it enhances sensitivity of thewater potential effector apparatus of the invention and enables sensingof subtle changes in the water potential.

FIGS. 11A and 11B show embodiments where the opening of the compressibleinsert is operatively engaged with a receiver through a diaphragm[1102]. The term “opening” refers to the area of contact When waterpermeates into the housing [1101] the volume of the VCM [1100]increases, thus building the turgor pressure inside the housing. Theincreasing pressure triggers compression of the insert [1105] (as seenin FIG. 11B), triggering an increase in the force applied to thediaphragm [1102] and, subsequently to the receiver [1103]. In someembodiments, the diaphragm is deformed in response to the force applied.In some embodiments, there is no diaphragm and the force is applieddirectly to the receiver. In some embodiments, the diaphragm'sdeformation closes a circuit.

FIGS. 9A and 9B show yet another embodiment where the opening of thecompressible insert [905] is oriented toward the bottom part of thehousing [901]. When water permeates into the housing [901] the volume ofthe VCM [900] increases, thus building the turgor pressure inside thehousing. The pressure triggers compression of the insert [905] (as seenin FIG. 9B), and an increase in the force applied to the diaphragm [902]and to the receiver [903]. In some embodiments, the force is applieddirectly to the receiver and there is no diaphragm.

In some embodiments, the VCM engages the receiver. In some embodiments,the insert engages the receiver. In some embodiments, the VCM and insertengage the receiver. In some embodiments, the receiver is configured toengage the VCM, insert, or both. In some embodiments, the receiverengages the VCM, insert or both at a predetermined threshold of waterconcentration. In some embodiments, the receiver engages the VCM, insertor both at a predetermined threshold of water potential. In someembodiments, only a defined area of the VCM or insert contact thereceiver or the diaphragm. In some embodiments, the insert contacts thereceiver or diaphragm and the area of contact is smaller than the areaof contact of the insert and VCM. A skilled artisan will appreciate thatby having a large area of contact between the VCM and the insert a smallchange in water concentration in the VCM will have an exponentiallylarger impact on the force exerted on the insert. If a uniform increasein VCM volume occurs around the full surface area of the insert even asmall increase will greatly affect the pressure inside the insert. Ifthe area of contact between the insert and the receiver is comparativelysmall than all this force will be applied at this small area. In thiswas a very small change in water concentration can result in a largeforce applied by the insert to the receiver. In some embodiments, theratio of the area of contact between the insert and VCM to the area ofcontact between the insert and the receiver is at least 2:1, 3:1, 4:1,5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1,50:1 or 100:1. Each possibility represents a separate embodiment of theinvention. In some embodiments, only a portion of the insert contactsthe receiver. In some embodiments, the apparatus comprises a rigidseparator that separates a portion of the insert, VCM or both from thereceiver, such that only a portion of the insert, VCM or both engagesthe receiver.

In some embodiments, the insert has a uniform thickness. In someembodiments, the insert has a uniform elasticity. In some embodiments,the insert compresses or inflates at the same rate uniformly across itssurface in response to a given pressure. In some embodiments, the insertis not uniform. In some embodiments, at least one part of the insertdeforms more easily in response to internal pressure. In someembodiments, at least one part of the insert deforms less easily inresponse to internal pressure. In some embodiments, the region of theinsert in contact with the receiver deforms more easily in response topressure. In some embodiments, the region of the insert in contact withthe receiver deforms less easily in response to pressure.

In some embodiments, the insert is surrounded by the VCM. In someembodiments, the entire length of the insert is surrounded by the VCM.In some embodiments, the insert is surrounded on three sides by the VCMand the fourth side contacts the receiver or diaphragm. In someembodiments, the insert is surrounded on three sides by the VCM and thefourth side contacts the housing. In some embodiments, the internalpressure of the insert and the pressure of the VCM with no water iscalibrated such that a predetermined increase in water concentration inthe VCM will result in an expansion of the VCM, insert or both necessaryto engage the receiver.

In some embodiments of the invention, the housing does not comprise acompressible insert. When water permeates the housing [101], the volumeof the VCM [100] increases, thus building the turgor pressure inside thehousing. When the VCM is fully swollen, or reaches a predeterminedthreshold, the force is applied to the diaphragm [102], which in turn,applies the force to the receiver [103]. Alternatively, there is nodiaphragm and the force is applied directly to the receiver.

In one embodiment, the concentration of the VCM in the housing is atleast 5%. In another embodiment, the concentration of the VCM is between5% to 90%. In one embodiment, the concentration of the VCM is between10% to 70%. In further embodiment, the concentration of the VCM isbetween 10% to 50%. In yet another embodiment, the concentration of theVCM is between 10% to 30%. In some embodiments, at least 5%, 10%, 15%,20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or90% of the space inside the housing is VCM. Each possibility representsa separate embodiment of the invention. In some embodiments, between5-90%, 10-90%, 15-90%, 20-90%, 5-85%, 10-85%, 15-85%, 20-85%, 5-80%,10-80%, 15-80%, 20-80%, 5-75%, 10-75%, 15-75%, 20-75%, 5-70%, 10-70%,15-70%, 20-70%, 5-65%, 10-65%, 15-65%, 20-65%, 5-60%, 10-60%, 15-60%,20-60%, 5-55%, 10-55%, 15-55%, 20-55%, 5-50%, 10-50%, 15-50%, 20-50%,5-45%, 10-45%, 15-45%, 5-40%, 10-40%, 15-40%, 20-40%, 20-45%, 5-35%,10-35%, 15-35%, 20-35%, 5-30%, 10-30%, 15-30%, or 20-30% of the spaceinside the housing is VCM. In some embodiments, the remained of thevolume is taken up by insert. In some embodiments, the inside space issubstantially free of empty space.

In an embodiment of the present invention, the VCM is a hydrogel. Insome embodiments, the VCM comprises a biocide. In some embodiments, thebiocide is a pesticide. In some embodiments, the biocide is anantibiotic. In some embodiments, the biocide kills at least one of mold,bacteria, spores and fungi. In some embodiments, the hydrogel is thebiocide.

In one embodiment, the hydrogel is made of homopolymers or copolymers ofacrylic acid, methacrylic acid, 2-Bromoacrylic acid, 2-(Bromomethyl)acrylic acid, 2-Ethylacrylic acid, Methacrylic acid, 2-Propylacrylicacid, Sodium acrylate, Sodium methacrylate and its derivatives, orsodium hydroxide or similar hydroxide blended with the monomers. In yetfurther embodiment the initial monomer concentration of 5-70% in a watersolution, is polymerized with a crosslinker of di-acrylate, ordi-acrylamide, or di-vinyl. In one embodiment, the crosslinkerconcentration is within the range of 0% wt/wt to 20% wt/wt. In oneembodiment, the formed polymer is a polymer of polyacrylic acid. Inanother embodiment the formed polymer is a polymer of sodium salt ofpolyacrylic acid.

In further embodiment of the invention, the hydrogel is made ofhomopolymers or copolymers of Alkylacrylamide,N-(3-Aminopropyl)methacrylamide hydrochloride, N-tert-Butylacrylamide,Diacetone acrylamide, N,N-Diethylacrylamide, N,N-Diethylmethacrylamide,N,N-Dimethylacrylamide, N-[3-(Dimethylamino)propyl]methacrylamide,N-Ethylacrylamide, N,N′-Hexamethylenebis (methacrylamide),N-Hydroxyethylacrylamide, N-(Hydroxymethyl)acrylamide,(4-Hydroxyphenyl)methacrylamide, 2-Hydroxypropyl-methacrylamide,N-(Isobutoxymethyl) acrylamide, N-Isopropylacrylamide,N-Isopropylacrylamide, N-Isopropylmethacrylamide, Methacrylamide and itsderivatives.

In one embodiment, copolymers of acrylic acid, acrylamide, maleicanhydride copolymer, polyvinyl alcohol copolymers, cross-linkedpolyethylene oxide, crosslinked carboxymethylcellulose and starchgrafted copolymer are used to control the hydrogel mechanicalproperties, and its swelling deswelling inside the limiting housing.

In yet another embodiment, the salt derivatives of acrylic acid are usedfor dry start. In another embodiment the hydrogel further comprisesfertilizer salt, pre-dissolved within the hydrogel. Addition offertilizer increases the osmotic pressure and triggering an increase ofat least 80% in swelling from dry state. Fast response of acrylamidederivatives is apparent in salt-rich soil due to the increased osmoticpressure.

In one embodiment, the hydrogel is configured to maintain its thermalstability. In one embodiment conjugated water molecule is present in thepolymer. Conjugated water in the polymer perform as antifreeze, loweringthe freezing temperature of the gel to −5° C. and keeping the hydrogelun-brittle. This temperature is relevant to any soil containing viableplants.

In some embodiments, the apparatus is operatively linked to anirrigation system. In some embodiments, the receiver signals to theirrigation system. In some embodiments, the irrigation system isactivated or shutoff by the apparatus. In some embodiments, theirrigation system activates or shuts off in response to the transducedsignal. In some embodiments, the signal shuts off the irrigation system.In some embodiments, lack of a signal activates the irrigation system.In some embodiments, when the receiver is not engaged it signals toactivate the irrigation system, and when the receiver is engaged itsignals to shutoff the irrigation system. In some embodiments, theapparatus is operatively linked to a soil water potential measuringsystem. In some embodiments, the apparatus is linked to a memory orstorage device. In some embodiments, the apparatus is linked to an aboveground readout or display.

In some embodiments, the apparatus is for use in moisture sensing. Insome embodiments, the apparatus is for use in measuring water potential.In some embodiments, the apparatus is for use in effecting waterpotential in water-containing media. In some embodiments, the apparatusis inserted in the water-containing media. In some embodiments, thewater-containing media is proximal to the apparatus. In someembodiments, the water-containing media is within 1, 2, 3, 4, 5, 7, 10,15, 20, 25, 30, 35, 40, 45 or 50 meters of the apparatus. Eachpossibility represents a separate embodiment of the invention.

In the context of the invention, water potential effector apparatusillustrated on FIGS. 2A-B, 3A-B, and 4A-B; has certain advantagesattributed to the compressible insert [201,301,401]. The advantages are,without limitation, improved durability; greater sensing capacity;resistance to extreme temperature conditions, such as frozen soil. Forexample, the compressible insert allows to control the pressure insidethe housing and to withstand sharp increase in VCM volume due tofreezing of the soil, thus preventing explosion of the housing. Theapparatus of the invention can therefore be inserted into the soilthroughout the year and retain its functionality under various climateconditions without any maintenance requirements. An additional advantageattributed to the compressible insert is shortening the time requiredfor the VCM to reach the transducer, and to therefore start generatingthe desirable output.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises” or“comprising,” when used in this specification, specify the presence ofstated features, integers, steps, operations, elements components and/orgroups or combinations thereof, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components and/or groups or combinations thereof. As usedherein the terms “comprises”, “comprising”, “includes”, “including”,“having” and their conjugates mean “including but not limited to”. Theterm “consisting of” means “including and limited to”.

As used herein, the term “and/or” includes any and all possiblecombinations or one or more of the associated listed items, as well asthe lack of combinations when interpreted in the alternative (“or”).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the specification andclaims and should not be interpreted in an idealized or overly formalsense unless expressly so defined herein. Well-known functions orconstructions may not be described in detail for brevity and/or clarity.

It will be understood that when an element is referred to as being “on,”“attached” to, “operatively coupled” to, “operatively engaged” with,“connected” to, “coupled” with, “contacting,” etc., another element, itcan be directly on, attached to, connected to, operatively coupled to,operatively engaged with, coupled with and/or contacting the otherelement or intervening elements can also be present. In contrast, whenan element is referred to as being “directly contacting” anotherelement, there are no intervening elements present.

It will be understood that, although the terms first, second, etc., maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. Rather, these terms areonly used to distinguish one element, component, region, layer and/orsection, from another element, component, region, layer and/or section.

Certain features of the invention, which are, for clarity, described inthe context of separate embodiments, may also be provided in combinationin a single embodiment. Conversely, various features of the invention,which are, for brevity, described in the context of a single embodiment,may also be provided separately or in any suitable sub-combination or assuitable in any other described embodiment of the invention. Certainfeatures described in the context of various embodiments are not to beconsidered essential features of those embodiments, unless theembodiment is inoperative without those elements.

Throughout this application, various embodiments of this invention maybe presented in a range format. It should be understood that thedescription in range format is merely for convenience and brevity andshould not be construed as an inflexible limitation on the scope of theinvention. Accordingly, the description of a range should be consideredto have specifically disclosed all the possible subranges as well asindividual numerical values within that range. For example, descriptionof a range such as from 1 to 6 should be considered to have specificallydisclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numberswithin that range, for example, 1, 2, 3, 4, 5, and 6. This appliesregardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to includeany cited numeral (fractional or integral) within the indicated range.The phrases “ranging/ranges between” a first indicate number and asecond indicate number and “ranging/ranges from” a first indicate number“to” a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numerals therebetween.

All publications, patent applications, patents, and other referencesmentioned herein are incorporated by reference in their entirety. Incase of conflict, the patent specification, including definitions, willprevail. In addition, the materials, methods, and examples areillustrative only and not intended to be limiting.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined by the appended claims and includes both combinations andsub-combinations of the various features described hereinabove as wellas variations and modifications thereof, which would occur to personsskilled in the art upon reading the foregoing description.

1. An apparatus comprising: a. a housing comprising at least one portion that is water permeable; b. a volume changing material (VCM) capable of retaining water, wherein said VCM increases or decreases its volume in response to increased or decreased water concentration respectively, and wherein said VCM is in direct contact with an inner surface of said at least one water permeable portion of said housing; c. a compressible insert configured to maintain at least a predetermined inner pressure within said apparatus; and d. a receiver configured to engage the VCM, compressible insert or both at or above a predetermined threshold of water concentration and configured to transduce a signal when engaged, when disengaged, or both.
 2. The apparatus of claim 1, wherein said VCM fills between 10-90% of the volume of space inside said housing.
 3. The apparatus of claim 1, wherein said compressible insert fills any space inside said housing not filled by said VCM.
 4. The apparatus of claim 1, wherein said receiver is configured to translate a force applied by said VCM, compressible insert or both into an electrical or mechanical signal.
 5. The apparatus of claim 1, wherein said receiver comprises a pressure sensor, a traveling sensor, a force sensor, a valve, or a gauge.
 6. The apparatus of claim 1, wherein said water permeable portion comprises a porous material.
 7. The apparatus of claim 6, wherein said porous media is a natural, synthetic, or a semi-synthetic membrane.
 8. The apparatus of claim 1, wherein the compressible insert comprises a gas-filled inner volume.
 9. The apparatus of claim 1, wherein the VCM comprises a hydrogel.
 10. The apparatus of claim 1, wherein the VCM comprises a biocide.
 11. The apparatus of claim 9, wherein the hydrogel is a biocide.
 12. The apparatus of claim 1, wherein the VCM comprises acrylic acid, methacrylic acid, 2-Bromoacrylic acid, 2-(Bromomethyl) acrylic acid, 2-Ethylacrylic acid, Methacrylic acid, 2-Propylacrylic acid, Sodium acrylate, Sodium methacrylate or derivatives thereof, sodium hydroxide, or homopolymers, heteropolymers or derivatives thereof polymerized with a crosslinker of di-acrylate, di-acrylamide, and di-vinyl.
 13. The apparatus of claim 1, wherein the VCM comprises Alkylacrylamide, N-(3-Aminopropyl)methacrylamide hydrochloride, N-tert-Butylacrylamide, Diacetone acrylamide, N,N-Diethylacrylamide, N,N-Diethylmethacrylamide, N,N-Dimethylacrylamide, N-[3-(Dimethylamino)propyl]methacrylamide, N-Ethylacrylamide, N,N′-Hexamethylenebis (methacrylamide), N-Hydroxyethylacrylamide, N-(Hydroxymethyl)acrylamide, (4-Hydroxyphenyl)methacrylamide, 2-Hydroxypropyl-methacrylamide, N-(Isobutoxymethyl) acrylamide, N-Isopropylacrylamide, N-Isopropylacrylamide, N-Isopropylmethacrylamide, Methacrylamide, or homopolymers, heteropolymers or derivatives thereof polymerized with a crosslinker of di-acrylate, di-acrylamide, and di-vinyl.
 14. The apparatus of claim 1, wherein the VCM comprises copolymers of maleic anhydride copolymer, polyvinyl alcohol copolymers, cross-linked polyethylene oxide, crosslinked carboxymethylcellulose or starch grafted copolymer.
 15. The apparatus of claim 1, further comprising a diaphragm between said VCM, insert or both and said receiver, wherein said diaphragm transfers force from said VCM, insert or both to said receiver.
 16. The apparatus of claim 1, wherein the apparatus is operatively linked to an irrigation system such that the irrigation system activates or shuts off in response to said transduced signal.
 17. The apparatus of claim 1, wherein the apparatus is operatively linked to a soil water potential measuring system.
 18. A method of measuring water potential by using the apparatus of claim
 1. 19. A method of effecting the water potential in water-containing media by using the apparatus of claim 1, wherein the water-containing media is proximal to the apparatus. 20.-22. (canceled) 